Johannes Fibiger, a Danish pathologist and bacteriologist who improved public health and revitalized cancer research, was born on this day in 1867. Early in his career, Fibiger discovered that there are two distinct forms of diphtheria, a disease that caused frequent epidemics in children and remains a problem in some parts of the world. Based on the finding, Fibiger developed an antidiphtheria serum that was successfully tested in 1897.

At the turn of the century, cancer research was stagnating because scientists did not know how to induce cancer in lab animals. In 1907, Fibiger noticed that some rats with tuberculosis had stomach tumors infested with tiny worms called nematodes. Intrigued, he investigated the source of the rats, a sugar refinery. After collecting roaches from the refinery, Fibiger fed them to rats that had been trapped elsewhere. When the first rat died, he found stomach cancer. For creating the first reproducible animal model of cancer, Fibiger received the Nobel Prize in medicine in 1926. He died 2 years later.